This investigation will examine the interactions between cell surface molecules and the extracellular matrix (ECM) along neural crest pathways. The goal of the proposed experiments is to elucidate the role of these cell-substratum interactions in neural crest migration and aggregation into ganglia. The neural crest is chosen as a model system because crest cells migrate extensively along pathways lined with extracellular matrix molecules; after migration, many crest derived cells form ganglia of the peripheral nervous system. Using an injection technique developed by the principal investigator, cells or latex beads can be implanted into embryos during neural crest migration. This method will be used: a. to inject latex beads with defined surface coats in order to probe neural crest pathways. b. to enzymatically disrupt the pathways and examine the subsequent effects on crest migration. c. to place neural crest and other cell types onto pathways they would not normally encounter. By injecting artificial probes, enzymes, and various cell types onto pathways followed by neural crest cells, one can probe in vivo many facets of neural crest morphogenesis. In addition, a laser microbeam will be use to ablate endogenous neural crest cells. This will allow us to examine the role of the neural crest in latex bead translocation and to examine the modifications to the ECM made by neural crest cells during migration. In order to study the cell-substratum events involved in gangliogenesis, an in vitro model system for examining aggregation of neural crest-derived ganglion cells has been developed. In these ways, the proposed experiments will combine tissue culture and experimental embryology to probe adhesive interactions involved in neural crest movement and gangliogenesis.